The general hypothesis is that there are discrete defects in the normal pathway of epidermal differentiation related to the phenotypic changes associated with genetic and acquired diseases of the epidermis, such as psoriasis, the ichthyoses and Darier's disease. The long-term focus of this research is defining those defects ultimately leading to safe and effective therapies for those disorders. Retinoids have profound effects on the normal and diseased epidermis and detailed studies of their action on three different representative steps in epidermal maturation is planned; differentiation limiting or modifying events involving a new human homeobox-containing gene Hox 1.1; modulation of the epidermal growth factor receptor (EGFR); and control of late events in terminal differentiation catalyzed by intracellular transglutaminases. The detailed specific aims are: 1) Determine the molecular mechanism regulating the response of the EGFR in cervical carcinoma cells ME-180 treated with retinoic acid (RA). The half-life of mRNA will be determined in control cells and after treatment with RA. Regulatory regions of the EGFR and other retinoid inducible genes will be transfected into ME-180 cells which are then treated with RA. A promoter from the EGFR gene of ME-180 cells will be ligated to CAT reporter gene constructs and transfected into normal keratinocytes and other epithelial cells and the response to RA quantitated. The mRNAs for retinoid nuclear receptors will be measured. Transcription factors controlling the RA response will be determined by gel retardation and footprinting assays. 2) Determining the role of human Hox 1.1 in normal and altered epidermal differentiation. The expression of Hox 1.1 in normal and altered epidermal differentiation. The expression of Hox 1.1 in normal and altered epidermal differentiation. The expression Hox 1.1 will be determined, by using in situ hybridization, in human fetal skin samples of different gestational ages and in human skin biopsies of normals, and patients with acne, psoriasis and genetics disorders of keratinization, and in patients treated with systemic and topical RA. Genomic clones for Hox 1.1 will be isolated and the 5' untranslated region of the Hox 1.1 gene will be characterized and sequenced. The detailed chromosomal mapping of the gene will continue. 3) Determine the genetic, biochemical and physiological relationships between the epidermal transglutaminases. Using the current transglutaminase cDNA clones from a human epidermis cDNA library full length cDNA will be produced and genomic transglutaminase characterized, especially its 5' nontranslated region. The promoter and enhancer sequences will be characterized looking for sequences known to be found in other epidermal genes responsive to retinoids and other pharmacological agents.